1. Field of the Invention
The invention relates to a mobile communications device, and more particularly to a mobile communications device with a compact-sized three-dimensional antenna.
2. Description of the Related Art
Internal antennas are increasingly popular and widely used in mobile communications devices (e.g. cellular phones). Recently, planner inverted F antennas (PIFAs) and monopole antennas have become available.
A planner inverted F antenna is required to be spaced apart from a circuit board of a mobile communications device at a predetermined vertical distance, and no electronic components are allowed between the planner inverted F antenna and the circuit board. However, the allotted antenna area and predetermined vertical distance are limited by the dimensions of the mobile communications device which is generally compact. As a result, the performance of the antenna measured in frequency width, radiation efficiency, and gain is hindered.
Similar with PIFAs, a monopole antenna is required to be spaced apart from a circuit board of a mobile communications device at a predetermined distance. However, the predetermined distance is horizontal, and also no electronic components are allowed between the monopole antenna and the circuit board. That is, a clearance zone is required between the monopole antenna and the circuit board to avoid negative disturbances to the monopole antenna. Generally, the clearance zone required by a monopole antenna exceeds 15 mm, a significantly large space when considering compact communication devices.